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    SubjectRe: [REPORT] kernel BUG at fs/ext4/inode.c:2620 - page_buffers()
    On Thu, Feb 17, 2022 at 11:08:38PM -0500, Theodore Ts'o wrote:
    > On Thu, Feb 17, 2022 at 05:06:45PM -0800, John Hubbard wrote:
    > > Yes. And looking at the pair of backtraces below, this looks very much
    > > like another aspect of the "get_user_pages problem" [1], originally
    > > described in Jan Kara's 2018 email [2].
    >
    > Hmm... I just posted my analysis, which tracks with yours; but I had
    > forgotten about Jan's 2018 e-mail on the matter.
    >
    > > I'm getting close to posting an RFC for the direct IO conversion to
    > > FOLL_PIN, but even after that, various parts of the kernel (reclaim,
    > > filesystems/block layer) still need to be changed so as to use
    > > page_maybe_dma_pinned() to help avoid this problem. There's a bit
    > > more than that, actually.
    >
    > The challenge is that fixing this "the right away" is probably not
    > something we can backport into an LTS kernel, whether it's 5.15 or
    > 5.10... or 4.19.

    Don't worry about stable backports to start with. Do it the "right way"
    first and then we can consider if it needs to be backported or not.

    thanks,

    greg k-h

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